1. Field of the Invention
This invention relates to passive radiators and audio loud speakers, in particular to the construction of same with minimization of flexure of the radiator and wobble minimization of the voice coil throughout the full range of inner and outer travel of the radiator during operation.
2. Description of the Related Art
In an audio speaker, or transducer, the closer together the points on the speaker frame, or basket, to which the suspension and spider are connected the greater the possibility of rocking, or wobble of the voice coil tube, or bobbin, with respect to the magnet during operation of the speaker. In a conventional speaker, the suspension is attached between the mouth of the basket and the outer diameter of the cone with the spider deeper in the basket beneath the surround. Wobble of the voice coil results from flexing of the speaker cone during operation as opposed to an even push or pull being exercised by the voice coil around the circumference where it connects to the speaker cone. When the cone is flexed, the upper end of the voice coil tube where it attaches to the cone and the lower end of that tube surrounding the magnet are no longer directly above each other with respect the central axis of the speaker. Stated another way, when wobble occurs the central axis of the voice coil bobbin momentarily is not coincident with the central axis of the speaker, i.e., the central axis of the voice coil bobbin is not parallel to the central axis of speaker. Thus, when the cone flexes and the voice coil bobbin wobbles, unwanted distortions occur in the sound waves being reproduced by the speaker. Such distortion effects are often audible to the listener. Since the human ear does not have a flat response to all frequencies, the audio frequency where the mechanical distortion occurs and the percentage of distortion created determines whether or not the distortion created is audible to the listener.
In U.S. Pat. No. 5,323,469, Scholz proposed the addition of a substantially conical stabilizing element between the underside of the speaker cone and the tube on which the voice coil is wound. In the Scholz configuration, the center of the cone is attached to the upper end of the voice coil tube and the conical stabilizing element is attached to the voice coil tube about one third the length of that tube below the connection point of the tube with the speaker cone. Additionally, a conventional spider is connected between the speaker frame and the voice coil tube at the point where the conical stabilizing element attaches to the voice coil tube. While this may present some improvement in the distortion level, the forces on the cone and voice coil presented by the spider remains uneven and can still produce flexing of the speaker cone resulting in differing degrees of distortion through out the travel of the cone and voice coil.